The invention concerns a pressure measurement device.
Such a pressure measurement device is known in which a magnet, which is designed as a permanent magnet, travels a corresponding to the pressure acting on an elastic measurement element. A Hall-effect sensor, referred to here as a Hall sensor, is exposed to the magnetic field of the magnet.
Essentially, two types of Hall sensors are known. A Hall sensor designed as a so-called linear sensor generates an analog sensor output voltage which is proportional to the magnetic flux perpendicular through the Hall plate of the Hall sensor. A Hall sensor designed as a so-called switch sensor is provided with an integrated comparator with predefined switch points and delivers a digital sensor output voltage. In a pressure measurement device that is provided with a Hall sensor, the sensor output voltage of the electric circuit of the pressure measurement device is further processed. In the case of a linear sensor, the electronic circuit delivers a voltage signal proportional to the pressure measured as an output signal. In this case, the pressure measurement device acts as a pressure measurement converter or a pressure teletransmitter. In the case of a switch sensor, the digital sensor output voltage can be applied to a semiconductor switch of the electronic circuit, which then delivers a switching signal as an output signal of the pressure measurement device. In this case the pressure measurement device is a pressure switch. The invention concerns both a pressure measurement device that operates as a pressure measurement converter or a pressure teletransmitter and a pressure measurement device that operates as a pressure switch.
The known pressure measurement device is a pressure measurement converter and delivers a device output signal proportional to the pressure measured. When both a pressure-proportional output signal and a switching signal are necessary, a second pressure measurement device must be provided to generate the switching signal. Even when two switching signals are necessary, this requires two separate pressure measurement devices according to the prior art.
A pressure measurement device with a Hall sensor operating as a pressure switch is known from U.S. Pat. No. 6,089,098. In this known pressure measurement device, the compressive force of a spring that holds a magnet in contact with a plate spring serving as a measurement element can be adjusted from the outside by means of a set screw. Also, in this known pressure measurement device the distance between the Hall sensor and the magnet can be adjusted by means of a set screw that is arranged entirely inside the pressure measurement device.
The object of the invention is to improve the generic pressure measurement device with the result that it can deliver more than one output signal.
A further object is to make the pressure measurement device adjustable and calibratible in a simple manner, preferably xe2x80x9con sitexe2x80x9d, i.e., at the use or installation site of the pressure measurement device.
The aforementioned object is accomplished according to the invention by means of the pressure measurement device according to claim 1 characterized in that at least a second Hall sensor is arranged to the side near the magnet outside of its path of movement on the sensor carrier and that the sensor output voltage of the second Hall sensor is further processed by the electronic circuit into a second output signal of the pressure measurement device.
It has been determined that when the path of movement of the magnet runs to the side near the first Hall sensor, at least one second Hall sensor can be associated with the magnet, which is also arranged to the side near the magnet outside its path of movement. The at least one second Hall sensor is mechanically and electrically independent of the first Hall sensor. The sensor output voltage of the second Hall sensor is further processed by the electronic circuit into a second output signal of the pressure measurement device. Each of the two Hall sensors can be designed either as a linear sensor or a switch sensor such that the pressure measurement device can deliver as output signals, for example, both a pressure-proportional output signal as a switching signal or two switching signals independent of each other. Because of the design according to the invention, this multifunctionality is obtained with only one elastic measurement element and only one magnet.
Provision can be made in an advantageous embodiment of the invention that the sensor carrier has a base plate and two guide rails attached on the inside of the base plate. Each Hall sensor is attached on a sensor mount that is displaceable along a path of movement on one of the guide rails that runs parallel to the path of movement of the magnet. A set screw is associated with each Hall sensor. The respective set screw has a threaded section and a cylindrical head section. The threaded section is in threaded engagement with the sensor mount, and the head section is pivotably mounted in the base plate immovable in the axial direction of the set screw, whereby the end of the head section is exposed on the outside of the base plate. In this manner, it is possible, from the outside, i.e., without opening the pressure measurement device, to adjust the setting of each of the two Hall sensors and thus to adjust the Hall sensor xe2x80x9con sitexe2x80x9d.
In an advantageous embodiment of the invention, provision can also be made that the sensor carrier has a base plate made of a light-permeable material and that a light-emitting diode that is arranged on the inside of the base plate is associated with each of the Hall sensors. The respective light-emitting diode serves, for example, to indicate the switch state of the associated Hall sensor and thus enables visual state monitoring xe2x80x9con sitexe2x80x9d. Since the base plate is made of a light-permeable material, the light of the light-emitting diode can penetrate outward through the base plate without the necessity of an opening or the like, which would render sealing the inside of the pressure measurement device difficult. Additional advantageous embodiments of the invention are defined in the dependent claims.